Mammalian protein kinases are important regulators of cellular finctions. Because disfunctions in protein kinase activity have been associated with several diseases and disorders, protein kinases are targets for drug development.
The tyrosine kinase receptor, FMS-like tyrosine kinase 3 (FLT3), is implicated in cancers, including leukemia, such as acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and myelodysplasia. About one-quarter to one-third of AML patients have FLT3 mutations that lead to constitutive activation of the kinase and downstream signaling pathways. Although in normal humans, FLT3 is expressed mainly by normal myeloid and lymphoid progenitor cells, FLT3 is expressed in the leukemic cells of 70-80% of patients with AML and ALL. Inhibitors that target FLT3 have been reported to be toxic to leukemic cells expressing mutated and/or constitutively-active FLT3. Thus, there is a need to develop potent FLT3 inhibitors that may be used to treat diseases and disorders such as leukemia.
The Abelson non-receptor tyrosine kinase (c-Abl) is involved in signal transduction, via phosphorylation of its substrate proteins. In the cell, c-Abl shuttles between the cytoplasm and nucleus, and its activity is normally tightly regulated through a number of diverse mechanisms. Abl has been implicated in the control of growth-factor and integrin signaling, cell cycle, cell differentiation and neurogenesis, apoptosis, cell adhesion, cytoskeletal structure, and response to DNA damage and oxidative stress.
The c-Abl protein contains approximately 1150 amino-acid residues, organized into a N-terminal cap region, an SH3 and an SH2 domain, a tyrosine kinase domain, a nuclear localization sequence, a DNA-binding domain, and an actin-binding domain.
Chronic myelogenous leukemia (CML) is associated with the Philadelphia chromosomal translocation, between chromosomes 9 and 22. This translocation generates an aberrant fusion between the bcr gene and the gene encoding c-Abl. The resultant Bcr-Abl fusion protein has constitutively active tyrosine-kinase activity. The elevated kinase activity is reported to be the primary causative factor of CML, and is responsible for cellular transformation, loss of growth-factor dependence, and cell proliferation.
The 2-phenylaminopyrimidine compound imatinib (also referred to as STI-571, CGP 57148, or Gleevec) has been identified as a specific and potent inhibitor of Bcr-Abl, as well as two other tyrosine kinases, c-kit and platelet-derived growth factor receptor. Imatinib blocks the tyrosine-kinase activity of these proteins. Imatinib has been reported to be an effective therapeutic agent for the treatment of all stages of CML. However, the majority of patients with advanced-stage or blast crisis CML suffer a relapse despite continued imatinib therapy, due to the development of resistance to the drug. Frequently, the molecular basis for this resistance is the emergence of imatinib-resistant variants of the kinase domain of Bcr-Abl. The most commonly observed underlying amino-acid substitutions include Glu255Lys, Thr315Ile, Tyr293Phe, and Met351Thr.
MET was first identified as a transforming DNA rearrangement (TPR-MET) in a human osteosarcoma cell line that had been treated with N-methyl-N′-nitro-nitrosoguanidine (Cooper et al. 1984). The MET receptor tyrosine kinase (also known as hepatocyte growth factor receptor, HGFR, MET or c-Met) and its ligand hepatocyte growth factor (“HGF”) have numerous biological activities including the stimulation of proliferation, survival, differentiation and morphogenesis, branching tubulogenesis, cell motility and invasive growth. Pathologically, MET has been implicated in the growth, invasion and metastasis of many different forms of cancer including kidney cancer, lung cancer, ovarian cancer, liver cancer and breast cancer. Somatic, activating mutations in MET have been found in human carcinoma metastases and in sporadic cancers such as papillary renal cell carcinoma. The evidence is growing that MET is one of the long-sought oncogenes controlling progression to metastasis and therefore a very interesting target. In addition to cancer there is evidence that MET inhibition may have value in the treatment of various indications including: Listeria invasion, Osteolysis associated with multiple myeloma, Malaria infection, diabetic retinopathies, psoriasis, and arthritis.
The tyrosine kinase RON is the receptor for the macrophage stimulating protein and belongs to the MET family of receptor tyrosine kinases. Like MET, RON is implicated in growth, invasion and metastasis of several different forms of cancer including gastric cancer and bladder cancer.
Because kinases have been implicated in numerous diseases and conditions, such as cancer, there is a need to develop new and potent protein kinase inhibitors that can be used for treatment. The present invention fulfills these and other needs in the art. Although certain protein kinases are specifically named herein, the present invention is not limited to inhibitors of these kinases, and, includes, within its scope, inhibitors of related protein kinases, and inhibitors of homologous proteins.